Collecting and storing cubes is a big part in a lot of FIRST competitions just this year alone (2018) we’ve seen it being used in FRC, FTC and now FGC. Our team built a cube collector for the 2018 FIRST Global Challenge , and I would like to show our approach to it , the challenges we’ve faced and how we solved them.
STEP 1 DESIGN:
Designing a cube collector isn’t as straightforward as one might think. The first thing we did was measure the size of the cubes and how many of them we would be holding at a time. After the measurements of the storage area were made we had to find out how to make the collector actually collect cubes. We were between using chain or poly-cord and ended using the chain for the first version. The first problem we ran into was making the chain turn inwards or outwards and because we were limited to only using one motor we came to the conclusion that if we made one part of the chain go over the other that would invert its motion.
STEP 2 BUILDING:
Since we were building this collector as part of the First Global Challenge we were limited to only using parts from the REV robotics robotics kit. The first thing we build was the part where the cubes would be stored. Because we were able to have only three cubes on the robot at a time we made the storage big enough to hold exactly three cubes.
Next we started working on the part that collected the cubes. Because we had already designed it this was quite a quick process despite of the complexity of the mechanism. The only challenge we faced on this part was how to get the chain tight so it would be functional.
The last step was installing the collector to the robot and creating a mechanism for it to be able to move up and down so we could collect and place cubes at different heights. To do this we mounted the mechanism to two extrusions from either of the back of the robot and using gearing we made it be able to go up and down. After that we realized that we needed to also have it so it wouldn’t go above or below certain thresholds to do this we attached a potentiometer to one of the axles holding the gears.
STEP 3 TESTING:
After rigorous testing we noticed that our lifting mechanism was becoming slower and more unreliable with time. After investigating we noticed that the axle spinning around made the hex port on the gear into a round one. We fixed this problem by changing the gears and used hex strengtheners so that it wouldn’t allow the axle to turn freely so it wouldn’t destroy the gear.
We also noticed that the chain was too heavy and cubes we’re this is why we replaced the chain with poly-cord.